This invention relates to a method for energy management of air-conditioning units, in particular air-conditioning units having a plurality of air-conditioning compressors.
In passenger cars and trucks having an internal combustion engine or an electric drive and a plurality of air-conditioning units, at least one air-conditioning compressor is used to produce cold air for each cooling circuit. The air-conditioning compressors are actuated immediately by the starting of the internal combustion engine. This results in the internal combustion engine or electric drive being loaded very heavily by the starting up of the air-conditioning compressors and almost stalling.
German document DE 199 60 079 A1 discloses a method for switching various classes of loads on and off by means of switching elements within the scope of an energy management operation which is carried out by a control device in a motor vehicle. The various classes of loads have various priorities, but it is possible to adapt the prioritization of the loads during ongoing operation, with the adaptation also taking into account the perceptibility of the operating states caused by a switching over operation. In this conventional method, for example, the air-conditioning compressor or compressors are switched off in the acceleration phase as loads with the lowest priority in order to prevent a braking effect. When there is a change in state, the individual load cannot be transferred to a class with a lower priority than the class in which it is in the normal state, i.e. when sufficient supply of energy is ensured in the usual travel mode. The switching takes place in such a way that individual loads of one class are switched, and the switching either takes place successively, with adaptation to the load state, or in parallel if a plurality of loads have to be switched for compensation purposes, or the entire class if necessary.
However, this energy management is carried out with dynamic adaptation of the priorities of individual loads only during operation. There is no indication whatsoever that, when at least one previously deactivated load is started or restarted, particular problems occur as a result of the starting up loading by loads, for example when air-conditioning compressors startup and restartup, or how these problems could be solved.
The object of the present invention is therefore to configure a method for energy management of air-conditioning units which considerably reduces the loading on the internal combustion engine or electric drive when the air-conditioning compressors start up, which prevents stalling and which makes subsequent adjustment by the engine electronics as comfortable as possible.
This object is achieved according to the invention by a method for energy management in air-conditioning units having the claimed features. Advantageous developments of the invention are also specified in the claims.
As a result of the method according to the invention for energy management of air-conditioning units, better compensation of the idling stability of an internal combustion engine or drive takes place. The engine/drive operates in a more stable fashion. Fluctuations in rotational speed or switch-on judder when switching on coolant compressors are or is minimized. This allows user comfort to be increased.
This and further objects, features and advantages of the present invention become apparent from the following description of a preferred exemplary embodiment of the invention in conjunction with the drawings.